The present invention relates generally to concentrated suspensions of polymers soluble in water, the preparation thereof and their use for the thickening of aqueous media.
Synthetic or natural organic polymers soluble or dispersable in water and which by solubilization or dispersion in water exhibit thickening and flocculating properties are widely used in industry in various fields of final application, such as in construction, paints, paper, textiles, cosmetics, the food industry, the treatment of waters, phytosanitation, mining, the assisted or secondary recovery of petroleum, etc.
For numerous applications, the polymers or hydrocolloids must first be prepared in the form of only slightly concentrated aqueous solutions or dispersions. It is known that the principal disadvantage of most of the powders of water soluble polymers is the difficulty of dissolving same rapidly without employing high shear agitation. Under the effects of excessively rapid hydration, the particles of the polymer in contact with water swell and tend to form clots or adhered masses resulting from the agglomeration of the particles. These clots, surrounded by a gelled thin film at the surface, are difficult to decompose and dissolve. The shear forces to which the polymer gels are exposed during their conversion to dilute aqueous solutions may cause the deterioration of certain of their advantageous properties.
To facilitate the dissolution of water soluble polymers of the polyacrylamide type, water-in-oil emulsions have been proposed which are prepared by the polymerization of the monomers in an emulsion and the resultant emulsion is inverted by the addition of water containing a surface active agent. However, these emulsions have very low stability, and tend to separate into two phases during storage.
Suspensions with a relatively higher concentration of polymers have also been proposed. Formulations of this type are described in U.S. Pat. Nos. 3,763,071 and 3,894,879.
However, these more concentrated suspensions are nevertheless not completely suitable for transportation, storage, metered pumping, etc. as a consequence of their attendant disadvantages resulting from deterioration, destabilization or sedimentation of the suspended polymers.